>>We RAR some directories into a single file on different spindle. Those single large files are picked up weekly via USB external (security concerns against on-the-wire-transfer)
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>Yes, but we need the differential only. This is sort of RoboCopy but over the Internet. So, at first, it is everything. Then, it is only what has changed (removal of items to be synchronized on the foreign location, addition of new items or adjustment of files which have been updated).


ACK that this is more sledge hammer than elegant. But it is a KISS approach where we are not dependant on all previous versions to be error free, so the worry of failing backup is minimized and the verification attempts as well ;-)

I'd hate to be one of the people realizing that some backup step misfired after the need for backup data is pressing.
One of my early brushes with such scenarios was in a now famous Italian bank here in F right after XMas and shortly before years end runs: during some building effort scheduled in the off-time a lot of the servers were physically impaired as well as backup storage "vault". The off-site redundant backup tapes had been freshly formated to be used again with that ending years data ;-)